The present invention relates to a process to enrich a gas in a liquid as well as to a device suitable for carrying out this process.
According to the state of the art, gases which are to be dissolved in liquids are fed by means of injection nozzles into a liquid volume or into the stream of a liquid. It is also a known procedure to feed gases via perforated hoses which are arranged under the water, applying a defined pressure of the gas to the hoses.
According to another method, a spraying head is employed to spray the water into a volume of a gas atmosphere that is sealed off from the environment, a process in which the drops of water are in a dissolution equilibrium with the gas phase prevalent around them. The water absorbs the gas and collects at the bottom of the tank from where it can be withdrawn for further utilization.
Such processes are employed, for example, to enrich water with oxygen when the water enriched with oxygen is to be used for on-site clean-up of soil contaminated with remnant pollutants. With these types of on-site clean-up operations, the enriched water is injected into the soil. The injection into the soil, however, is preceded by other water preparation processes. Thus, for instance, the water employed for on-site clean-up passes through biological filters and chemical treatment stages which serve to optimize the composition of the water utilized for the on-site clean-up. The water that is thus incorporated into the soil is removed again at another site and then fed to a circulation process for renewed enrichment with oxygen and of chemical-biological treatment.
In order to achieve optimum functioning of an on-site clean-up system as well as to achieve optimum clean-up results, it is necessary to ensure an oxygen concentration in the water which can fulfill the technical requirements. In this manner, downstream stages of a water-treatment installation, for instance, operate with fewer malfunctions if an oxygen concentration is maintained which lies below the saturation value at an operating pressure that is above atmospheric pressure.
The pressure or throughput volume with which the cartridges and filters are operated must also be adapted to the requirements at hand. Since the oxygen atmosphere of the tank through which the water to be enriched trickles is constantly losing oxygen during the enrichment process, the tank must be charged with an overpressure in order to ensure a continuous feed of oxygen into the water as well as to prevent a backflow of the water.
If oxygen is fed by means of injection nozzles into the water to be used for on-site clean-up, excess oxygen escapes into the environment and must then be returned to the oxygen tank via circulation systems, or else it must be disposed of as waste gas since it is loaded with pollutants as the result of its flowing through the circulation system. The use of perforated hoses is not very suitable because they have to be laid flat for purposes of gassing in order to prevent a fusing of the individual gas bubbles. For this reason, this method requires a great deal of space.
The use of tanks charged with an oxygen atmosphere and fitted with a spraying head which atomizes the water to be enriched with oxygen in the tank regularly leads to saturation of the water with oxygen. Thus, it is not possible to regulate the oxygen concentration in the water to concentrations below the saturation value at atmospheric pressure.
In order to achieve the water pressure needed for the operation of the installation, the oxygen pressure above the water level must be kept at such a value that there is an over-saturation--relative to the atmospheric pressure--of the water with oxygen which exceeds the concentration that is acceptable for the overall process.